This project deals with the interactions of tobacco mosaic virus and its components: virus-virus interactions, protein-protein interactions, RNA-RNA interactions, protein-RNA interactions and the interactions of the virus and its components with ions, with organic molecules and with other proteins. Of special concern is the energetics of TMV protein polymerization. Plans for the coming year include a comparative study of the polymerizaiion of coat proteins from strains of TMV, especially those with known differences in amino acid composition leading to a net charge different from that of type strain coat protein. Other plans include specific ion binding studies, especially calcium ion binding, by virus, polymerized protein RNA, and, an investigation of comformational changes associated with virus protein polymerization and an attempt to explain certain peculiarities in the electro-optical behavior of tobacco mosic virus preliminary to a study of polymerization of TMV protein by electro-optical means.